An optical network is a technology for effectively providing a necessary band to a network unit, and has a point-to-point structure and a point-to-multipoint structure. An optical line terminal (OLT) has an interface for supporting a plurality of optical network units (ONU), and has a control authority for the entire ONUs. In general, the point-to-point structure is mainly used in an active optical network (AON), and the point-to-multipoint structure is mainly used in a passive optical network, and the point-to-point structure and the point-to-multipoint structure are standardized by an international standardization organization, such as IEEE and ITU-T.
FIG. 1 is a configuration diagram of a general PON system.
As illustrated in FIG. 1, the PON system generally has a tree structure in which one OLT 101 corresponds to a plurality of ONUs 105 to 107 as a ratio of 1:N through a passive element 103. In downstream transmission to the ONUs 105 to 107 in the OLT 101, data transmitted by the OLT 101 is broadcasted to the entire ONUs 105 to 107, so that a problem due to media sharing is not generated. However, in a case of upstream transmission, the plurality of ONUs 105 to 107 is connected to the OLT 101 through one optical fiber from the passive element 103, so that a time division multiple access medium access control (TDMA MAC) protocol using a transmission media while avoiding temporal overlap is necessary in order to perform the upstream transmission without a collision between the ONUs 105 to 107.
In the meantime, according to the XGPON standard established by the ITU-T, in order to embrace traffic having various characteristics, each ONU stores and transmits upstream data according to a priority by setting a separate class queue called T-CONT (transmission container) for each service class. The OLT may effectively use a band by collecting standby state information regarding the number of standby user packets in a corresponding queue from the ONT for the T-CONTs operated in the entire PON links managed by the OLT, and allocating an upstream band width for each T-CONT based on the collected standby state information.
As described above through the ITU-T XGPON standard, the upstream transmission the passive optical network (PON), especially, the PON based on the TDMA, is performed in a method in which the ONU first makes a report of a quantity of user packets stacked in the ONU queue to the OLT, the OLT determines upstream bands for the entire ONUs based on the report and allocates the determined upstream band to each ONU, and thus the ONU transmits data within the allocated band in response to the allocation.
When the specific ONU reports that a quantity of user packets is larger than the quantity of user packets standing by in the actual queue, or reports that the queue always seems to be fully filled regardless of the quantity of actual user packets in this structure, the OLT determines the upstream band of each ONU and allocates the determined upstream band while depending on the corresponding report, thereby resulting in unnecessary waste of the upstream band width.
When the ONU making a queue report error is present in the network as described above, a part of or an entire upstream bandwidth is unnecessarily occupied, and as a result upstream transmission of another normal ONU is disturbed. This causes a similar result to a rogue ONU in which an optical module of the specific ONU disturbs the upstream transmission of other ONUs by creating an abnormal operation. Accordingly, a method and an apparatus for detecting the queue report error of the ONU to take measures for the ONU, which transmits an incorrect queue report, are necessary.